Peter Spinks

Feeling the buzz: Bees pollinate the flowers of at least one third of wild and farmed plants but their numbers are dropping due, in part, to a parasite varroa destructor which has now reached New Zealand and Papua New Guinea.

Honeybees lead something of a charmed life, as they flit about collecting nectar and pollen and producing oodles of honey and wax. But now, it seems, their carefree days might soon be numbered.

Populations of the four-winged insects, which pollinate the flowers of at least one-third of wild and farmed plants that humans eat, have decreased over the past three decades in the US and Britain. In part, this has been due to the prevalence of crop pesticides, the destruction of flower-rich habitats and pests.

The biggest pest threat is from a pinhead-sized parasite, Varroa destructor, an oval-shaped, reddish-brown mite that sucks the blood from bees and inflicts upon them a suite of virulent diseases, such as deformed-wing virus.

Australia is one of the last countries to remain free of the pernicious bloodsuckers. Neighbouring New Zealand and Papua New Guinea have been less fortunate, raising the prospect that Australia will be next to fall prey to a mite invasion.

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"Leading experts agree that it is not a matter of if but when," says Bendigo-based apiculturist Jody Gerdts. "Varroa will eventually get here. Lots of money and resources have been dedicated by government and bee-reliant industries to prolong the inevitable."

Sydney University social insect expert Madeleine Beekman shares this view. "The expectation is that Varroa will get to Australia at some stage," Dr Beekman says. "It is thus important we are proactive and prepare for its arrival."

This does not augur well for horticulture in general: the mites could decimate Australia's population of wild honeybees, leaving crop growers without their biggest and free source of pollination.

The garden state

Varroa mites could enter the country in a variety of ways and, on several occasions, the quarantine authorities have been lucky to intercept them before they ducked through. Victoria, in particular, is vulnerable.

"The ports of Melbourne, Geelong, and Portland are considered extremely high risk ports of entry for this pest," Ms Gerdts explains. "Ships and planes arrive at these ports from all over the world and sometimes they carry hitchhiking swarms of bees. Any one of these swarms could carry Varroa – it only takes one mite to start an incursion."

Fortunately, she points out, apiary officers at Victoria's Department of Environment and Primary Industries have an extensive surveillance and monitoring program around these ports.

"Any swarms are reported and inspected for Varroa and other bee pests that we do not currently have in Australia," she says. "They also maintain honeybee colonies at these ports as sentinel hives that are monitored every six weeks for bee pests."

Victoria has an emergency response plan in case Varroa mites arrive here. "Their primary goal is to eradicate the threat before it becomes established in honeybee colonies," Ms Gerdts adds.

"One reason why all honeybee diseases and parasites spread so easily is the beekeepers' practice of moving their colonies around to where the flowers are," Dr Beekman explains. "Thus, if there's a huge crop, beekeepers from other parts of the country place their colonies in the vicinity of that crop – thereby facilitating the movement of diseases and parasites."

Bees, as she points out, are prone to making mistakes – and often end up in the wrong colony.

In perspective

During the late 1970s and early 1980s, colonies of the Asian hive bee, Apis cerana, and its secondary host, the Western honeybee, Apis mellifera, were introduced to Irian Jaya from Java. The Asian bees brought with them a parasitic mite similar to Varroa, as did the other honeybees.

It was feared that the mites would eventually spread to the main beekeeping areas of Papua New Guinea and destroy the nation's fledgling bee industry; additionally it was believed that the mites could island-hop through the Torres Strait to Australia.

When Varroa mites were first described, they were called Varroa jacobsoni. "It was assumed that all mites were of the same species," Dr Beekman says. "We do not know exactly when the mite decided to move from A. cerana on to A. mellifera, but this was made possible by beekeepers and bee researchers moving colonies around."

Before human-assisted movements, the two bee species were geographically separated. During the 1960s, mites from A. cerana moved on to A. mellifera which resulted in the new species of Varroa destructor.

"Varroa destructor is only known from A. mellifera where it causes harm," Dr Beekman explains. "As far as we know, Varroa jacobsoni does not cause harm to its original host, A. cerana."

Another species-jump occurred recently in Papua New Guinea. "Once a population of mites becomes isolated – in this case because it moved to another species of bee – it will evolve into a different species because it no longer mixes with the original population."

Control

In addition to existing monitoring programmes, the race is on to find revolutionary ways of disabling them before they wreak havoc on wild and domestic bee strains.

Among other things, biotechnologists have been sequencing the mite's genome, or genetic makeup. Biotechnology can knock out critical genes that the mite needs for its survival. If this is achieved, then control might be possible. The work could assist research being carried out in Britain on a limited budget, which is not yet completed.

Once the genome sequence is complete, researchers will create and scour databases of all the Varroa genes in a bid to identify those that can be used to disable the mites before they inflict their damage.

Practical steps

The Livestock Disease Control Act (1994) requires beekeepers that suspect Varroa mites are present in their apiaries, to notify a government apiary, animal health or veterinary officer. They can do this by calling 1800 675 888.

Until an officer arrives, beekeepers are advised to take the following steps to reduce the risk of spread: A specimen of the suspect mite should be placed in a small jar of methylated spirits. The jar should be kept in a cool, safe place and away from sunlight.

A specimen of the suspect mite should be placed in a small jar of methylated spirits. The jar should be kept in a cool, safe place and away from sunlight.

The opened hive should be reassembled and closed.

The hive and lid should be marked with one identification number or name.

Hands, gloves and hive tools should be thoroughly washed to ensure the mite is not carried from the apiary.

To find out why introduced species can become so destructive in new areas, read the article "Can behavioral and personality traits influence the success of unintentional species introductions?" by David Chapple, Sarah Simmonds and Bob Wong at: www.sciencedirect.com/science/article/pii/S0169534711002709

Please send bright ideas for new topics to pspinks@fairfaxmedia.com.au

5 comments

Again Australia is under threat from introduced species, the Varroa destructor mite is expected to attack Australian bees similar to that which is happening overseas (USA, New Zealand, Papua New Guinea). This article outlines the preparations that are going on in Australia to meet this threat.

Commenter

Bob

Date and time

September 02, 2014, 10:14AM

Actually Bob, these bees aren't Australian, they themselves are introduced and invasive. Yes costly to replace them as agricultural pollinators if Varroa arrives, but there are 2000+ species of native bees that are natural pollinators. The introduced Honey Bees are aggressive and destructive to a lot of these natives. Our natives our not susceptible to Varroa and many could be used as alternative pollinators for agriculture.

Commenter

B

Date and time

September 02, 2014, 5:18PM

Dont worry our scientists are ready for the assault, awash with funds from the latest Budg........oh wait........guess we had better all pray to God - and make sure its Tony's god (Murdoch/Rinehart) or they wont listen.

Commenter

Mark

Location

melbourne

Date and time

September 02, 2014, 5:14PM

The greater threat to the bees is the neonicotinoid class of insecticides in widespread use in agriculture and home gardens, which is weakening bee colonies and making them more susceptible to other threats - like this mite. Even if you don't really like bees, but quite like birds, or even are fond of people, this is really important to be aware of, and to share, because no bees = no food = no us! Please, don't use Confidor in your garden, or believe Bayer's spin about it being non-toxic to bees. It's target is lacewing insects - usually thrips - of which bees are one, and they are suffering massive collateral damage.Members of the general public can't do much to protect against the arrival of varroa, but you can however work towards giving the bees the best possible chance at surviving it. You can read more here: http://news.nationalgeographic.com.au/news/2014/07/140709-birds-insects-pesticides-insecticides-neonicotinoids-silent-spring/

Commenter

willowoodhoney

Date and time

September 02, 2014, 6:01PM

All we need is another idiot like the one who illegally introduced the bumble bee into Tasmania from NZ.It's sadly only a matter of time. The Govt spends Millions on Terrorism and human border control yet is reducing the amount spent on quarantine, dumb.

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